Tunable Dielectric and Thermal Properties of Oxide Dielectrics via Substrate Biasing in Plasma-Enhanced Atomic Layer Deposition

Abstract

The ability to control the properties of dielectric thin films on demand is of fundamental interest in nanoscale devices. Here, we modulate plasma characteristics at the surface of a substrate to tune both dielectric constant and thermal conductivity of amorphous thin films grown using plasmaenhanced atomic layer deposition. Specifically, we apply a substrate bias ranging from 0 to ∼117 V and demonstrate the systematic tunability of various material parameters of Al 2 O 3 . As a function of the substrate bias, we find a nonmonotonical evolution of intrinsic properties, including density, dielectric constant, and thermal conductivity. A key observation is that the maximum values in dielectric constant and effective thermal conductivity emerge at different substrate biases. The impact of density on both thermal conductivity and dielectric constant is further examined using a differential effective medium theory and the Clausius−Mossotti model, respectively. We find that the peak value in the dielectric constant deviates from the Clausius−Mossotti model, indicating the change of oxygen fraction in our thin films as a function of substrate bias. This finding suggests that the increased local strength of plasma sheath not only enhances material density but also controls the dynamics of microstructural defect formation beyond what is possible with conventional approaches. Based on our experimental observations and modeling, we further build a phenomenological relation between dielectric constant and thermal conductivity. Our results pave invaluable avenues for optimizing dielectric thin films at the atomic scale for a wide range of applications in nanoelectronics and energy devices.

Influence of substrate biasing on structural, chemical and electrical properties of Al2O3 thin films deposited by PEALD

“…In figure 2(b), it can be seen that the mass density reaches its maximum at 5 W, and decreases when the substrate bias reaches 10 W and then becomes stable at higher power. These results are in good agreement with the studies reported by Kim et al [30], which show that the mass density reached a maximum (3.1 g cm −3 ) when biasing the substrate with an RF power source voltage at 20 V. The decrease of the mass density with ion bombardments has been attributed to the increase of the incorporation of impurities, such as carbon and hydrogen into the Al 2 O 3 film [28]. The hydrogen content is mostly contributed as OH groups in the film deposited by PEALD [28,32,33].…”

“…They also found that the properties of SiN x films were degraded. Kim et al [30] have demonstrated the modulation of both dielectric and thermal characteristics of Al 2 O 3 thin films using substrate biasing in PEALD. In our previous work [31], we have shown that substrate biasing can be used for simultaneous tuning of film quality and dielectric properties of aluminium nitride (AlN) thin films.…”

Foundations of atomic-level plasma processing in nanoelectronics

“…Next, we discuss the influence of ions during PE-ALD. In several studies on PE-ALD of oxides as well as nitrides [186,[210][211][212][213][214][215][216][217][218], a significantly beneficial influence of ions has been reported, such as impurity removal, densification [219], and crystallization (illustrated in figure 11(C2)). On the other hand, unfavorable effects such as sputtering, amorphization, and impurity implantation (illustrated figure 11(C3)) can be present when the supplied ion energy or dose is too high [186,193].…”

Comparative Study of Plasma-Enhanced-Atomic-Layer-Deposited Al2O3/HfO2/SiO2 and HfO2/Al2O3/SiO2 Trilayers for Ultraviolet Laser Applications

“…Exciting progress has been made in the PEALD growth of oxides, such as ZrO 2 , HfO 2 , SiO 2 , TiO 2 , and Al 2 O 3 . Parameters including plasma composition, ion dose, and substrate bias − were studied to improve the material and interface properties in electronic devices. PEALD-grown HfO 2 single-layer thin films, SiO 2 single-layer thin films, as well as HfO 2 and SiO 2 pairs for AR and high-reflective (HR) thin films have been studied specifically for laser applications.…”